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<body class='hmmessage'><div dir='ltr'>It's interesting to see that the qualifying paragraph that Phil quotes here:<div><br></div><div><i> "Ofcom will endeavour to meet applicants’ coverage aspirations where <br>possible, subject to frequency availability and the impact of the trial <br>multiplexes on other spectrum users."</i></div><div><br></div><div>is precisely the sentiment implied in the original formula for Community Radio - which Ofcom has since backed off to the infamous "25 plus 25 and 5km radius" guideline.</div><div><br></div><div>--------------------------------------</div><div><br><br><div>> Date: Mon, 9 Mar 2015 08:51:12 +0000<br>> From: lists@philedmonds.info<br>> To: cma-l@mailman.commedia.org.uk<br>> Subject: Re: [cma-l] DAB trials<br>> <br>> Where does this 100watt "limit" come from? If you delve far enough into <br>> the Ofcom published "Invitation to apply" document, are these lines:<br>> <br>> "We anticipate that transmitters will usually operate at a maximum power <br>> of 100 watts for this trial period. This is because the impact on other <br>> spectrum users is likely to increase as the power level increases above <br>> this level, and the amplifiers that Ofcom will provide are specified to <br>> operate up to this power level."<br>> <br>> Furthermore:<br>> "Ofcom will endeavour to meet applicants’ coverage aspirations where <br>> possible, subject to frequency availability and the impact of the trial <br>> multiplexes on other spectrum users."<br>> <br>> Which means to me they won't rule out more than 100 watts power, but the <br>> onus would be on the applicant to justify this. This would naturally <br>> need some technical acumen to do, but as this is as much a "engineering <br>> trial" as anything else one would assume that this would be a given.<br>> <br>> You don't have to use Ofcom's kit, you can provide your own, obviously <br>> you'd need to provide your own if you got more than 100 watt allocated.<br>> <br>> So simple answer - Ofcom have come up with 100 watt "expectation" of <br>> maximum power as this is what the kit they've got supports.<br>> <br>> Phil.<br>> <br>> <br>> On 08/03/2015 18:36, fantasy office wrote:<br>> > Whilst we're delving deeply into the theory of RF propogation, I suggest<br>> > there could be another reason for Ofcom's suggesting 100 watts. Clearly,<br>> > to acheive 10km radius at 220MHz, you'll need more power than 5km at<br>> > 100MHz. So, perhaps Ofcom have 'sourced' a handful of 100 watt models,<br>> > which will be OK for this trial, which is all guesswork anyway.... It<br>> > has to be, as there are so many unknown quantities.<br>> ><br>> > Most importantly, whatever comes of this trial, it'll be an awful lot of<br>> > work for a handful of people. The most important consideration must be<br>> > 'how does this affect the listener?' and how will it benefit our<br>> > station? Probably the most overlooked questions in all of this debate.<br>> ><br>> ><br>> > Phil Dawson<br>> > FANTASY RADIO 97FM<br>> > Devizes ,<br>> > Wiltshire<br>> ><br>> ><br>> > On 08/03/2015 16:21, cma-l-request@mailman.commedia.org.uk wrote:<br>> >> Send cma-l mailing list submissions to<br>> >> cma-l@mailman.commedia.org.uk<br>> >><br>> >> To subscribe or unsubscribe via the World Wide Web, visit<br>> >> http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br>> >> or, via email, send a message with subject or body 'help' to<br>> >> cma-l-request@mailman.commedia.org.uk<br>> >><br>> >> You can reach the person managing the list at<br>> >> cma-l-owner@mailman.commedia.org.uk<br>> >><br>> >> When replying, please edit your Subject line so it is more specific<br>> >> than "Re: Contents of cma-l digest..."<br>> >><br>> >><br>> >> Today's Topics:<br>> >><br>> >> 1. Re: Ofcom announces trials to help small stations join<br>> >> digitalradio - 100w limit (Tony Bailey)<br>> >><br>> >><br>> >> ----------------------------------------------------------------------<br>> >><br>> >> Message: 1<br>> >> Date: Sun, 08 Mar 2015 15:58:21 +0000<br>> >> From: Tony Bailey <ravensound@pilgrimsound.co.uk><br>> >> To: cma-l@mailman.commedia.org.uk<br>> >> Subject: Re: [cma-l] Ofcom announces trials to help small stations<br>> >> join digitalradio - 100w limit<br>> >> Message-ID: <54FC719D.6080100@pilgrimsound.co.uk><br>> >> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed"<br>> >><br>> >> Ofcom states that the coverage limit is set at 40% of the "corresponding<br>> >> local DAB multiplex area" and that a practical limit of 100 W ERP "may<br>> >> achieve a service area of approximately 10 km radius". A synchronised<br>> >> two tx (not repeater) system would be spaced at no more than 15 km<br>> >> apart. As pointed out below, this has to based on a practical antenna<br>> >> situation to have any relevance.<br>> >><br>> >> Tony Bailey<br>> >><br>> >> On 08/03/15 14:01, Ian Hickling wrote:<br>> >>> It seem there's a lot of second-guessing going on here from people who<br>> >>> may know a lot about administration and encoding but possibly not so<br>> >>> about the black magic that is RF propagation.<br>> >>> There's no point in trying to relate 100W ERP to 5km for Band III DAB<br>> >>> - just as it's equally irrelevant to relate 25W with FM to 5km - sorry.<br>> >>> Topography, geology, refraction, refraction, foliation, antenna<br>> >>> efficiency and launch conditions have far too large an influence.<br>> >>> In terms of propagated signal transit, there's not a huge difference<br>> >>> in practical terms between FM at say 100 MHz and DAB at 200 MHz when<br>> >>> you take into account antenna size, efficiency, reflection and<br>> >>> refraction.<br>> >>> Because of the difference between demodulation formats, a receiver<br>> >>> can tolerate a much lower signal level on DAB than on FM to resolve an<br>> >>> acceptable audio service.<br>> >>> This was originally proposed at 20dB from the point of view of<br>> >>> transmitted power but then revised to 10dB - meaning that a DAB<br>> >>> transmitter in Band III would need one tenth of the ERP of an FM<br>> >>> transmitter in Band II to achieve the same audience.<br>> >>> Hence it is puzzling why Ofcom has set so high a required signal level<br>> >>> for a DAB service area of the order of 72dBuV/m as opposed to 54<br>> >>> dBuV/m for FM.<br>> >>> Beware - there is a distinct difference between a Power Decibel in<br>> >>> transmission and a Voltage Decibel in reception!<br>> >>><br>> >>> Let's not invoke DAB+ and DRM - Ofcom specifically rules them out in<br>> >>> 2.30 and 2.32<br>> >>><br>> >>> Yes, Block 5A would be ideal as it's relatively clear, allocated and<br>> >>> accessible to modern receivers - but Ofcom apparently doesn't accept<br>> >>> that as it hasn't headed straight for it.<br>> >>><br>> >>> As I've protested many times, there is technically nothing at all to<br>> >>> prevent a standalone transmitter radiating a single programme stream<br>> >>> to serve a discrete area either on DAB, DAB+ or DRM as far as I'm<br>> >>> aware. If I'm wrong I'd appreciate the exact reasons why.<br>> >>><br>> >>> Looking at only the RF component in the transmission chain, several UK<br>> >>> manufacturers could offer a 2U Band III 300W unit at around ?2000 if<br>> >>> the demand were high enough - no real cost differences from today's<br>> >>> Band II units.<br>> >>><br>> >>> Let's not get distracted - the encoding is software-defined - the<br>> >>> actual RF transmitter is not!<br>> >>><br>> >>> Ian<br>> >>><br>> >>> ------------------------------------------------------------------------<br>> >>> Date: Sun, 8 Mar 2015 11:13:25 +0000<br>> >>> Subject: Re: [cma-l] Ofcom announces trials to help small stations<br>> >>> join digitalradio - 100w limit<br>> >>> From: alan.coote@5digital.co.uk<br>> >>> To: tlr@gairloch.co.uk; transplanfm@hotmail.com; info@a-bc.co.uk<br>> >>> CC: cma-l@mailman.commedia.org.uk<br>> >>><br>> >>> I can't help thinking that someone at Ofcom ran the simulations and<br>> >>> came up with 100W = 5km radius.<br>> >>><br>> >>> Therefore if small scale DAB became a reality it wouldn't annoy Radio<br>> >>> Centre too much (they'd still complain as that's their mentality) and<br>> >>> at worst secondary legislation could make it happen.<br>> >>><br>> >>> Kind Regards<br>> >>><br>> >>> Alan<br>> >>><br>> >>><br>> >>> Hear Alan Every Week on Let's Talk Business The UK's Premier Radio<br>> >>> Programme For Current and Future Entrepreneurs - Now Broadcast To Over<br>> >>> 5 Million People <http://www.letstalkbusinessonline.com/><br>> >>><br>> >>><br>> >>> From: "tlr@gairloch.co.uk <mailto:tlr@gairloch.co.uk>"<br>> >>> <tlr@gairloch.co.uk <mailto:tlr@gairloch.co.uk>><br>> >>> Reply-To: "tlr@gairloch.co.uk <mailto:tlr@gairloch.co.uk>"<br>> >>> <tlr@gairloch.co.uk <mailto:tlr@gairloch.co.uk>><br>> >>> Date: Sunday, 8 March 2015 00:45<br>> >>> To: "transplanfm@hotmail.com <mailto:transplanfm@hotmail.com>"<br>> >>> <transplanfm@hotmail.com <mailto:transplanfm@hotmail.com>>, Associated<br>> >>> Consultants <info@a-bc.co.uk <mailto:info@a-bc.co.uk>><br>> >>> Cc: "cma-l@mailman.commedia.org.uk<br>> >>> <mailto:cma-l@mailman.commedia.org.uk>" <cma-l@mailman.commedia.org.uk<br>> >>> <mailto:cma-l@mailman.commedia.org.uk>><br>> >>> Subject: Re: [cma-l] Ofcom announces trials to help small stations<br>> >>> join digitalradio - 100w limit<br>> >>><br>> >>> I simplistically presumed they settled on the 100W suggested limit on<br>> >>> the basis that at the Band III frequencies of DAB it would give<br>> >>> roughly the same coverage area (at 58dBuV/99%) as 25W on Band II (at<br>> >>> 54dBuV/90%).<br>> >>> NB the average *local* DAB multiplex power is 1.3kW, not 2kW, but of<br>> >>> course they tend to be from sites with much higher antennas than<br>> >>> economically available to community stations, so the chances are the<br>> >>> 100W represents an even tinier coverage area in comparison to current<br>> >>> local multiplexes than might appear at first sight from a simple<br>> >>> comparison of powers. But I can see it is much easier for Ofcom to<br>> >>> control the allowed power than to get into arguments over exact<br>> >>> percentages of area covered. Maybe 500W would have been more realistic<br>> >>> if they wanted to take that simplistic approach, with a lower limit<br>> >>> applied in the few cases where 500W coud cause difficulties.<br>> >>> (I guess there is also the question that Ofcom is paying for the<br>> >>> transmitters in the trial, and a band III amplifier running at , say,<br>> >>> 250W is a lot more expensive than a 50W one, especially if one uses<br>> >>> the technique of greatly underrunning a much higher power design to<br>> >>> help achieve the necessary linearity.).<br>> >>> Seems to me that block 5A, (currently unused, but allocated for local<br>> >>> DAB) could be used as a UK-wide frequency block for terrain limited<br>> >>> single station services up to 500W to deal with all the areas where<br>> >>> there is a low density of local stations (ie only one within the<br>> >>> interference range of a 500W TX) and it could be done tomorrow,<br>> >>> without any fancy trials or risk of interference, clearing out one<br>> >>> whole tier of demand without any fuss, leaving trials and more<br>> >>> complicated sharing and co-channel planning issues to be threshed out<br>> >>> over time in the other seven frequency blocks allocated to local<br>> >>> ensembles in areas of more dense demand. It's also much lower in<br>> >>> frequency than the other blocks, which reduces the demands on the<br>> >>> low-cost software defined transmitter.<br>> >>> Alex<br>> >>><br>> >>> On 25 February 2015 at 13:04 Associated Broadcast Consultants<br>> >>> <info@a-bc.co.uk <mailto:info@a-bc.co.uk>> wrote:<br>> >>><br>> >>> We challenged the 100w limit in the consultation - suggesting that<br>> >>> the "no greater than 40% of the local commercial Mux area" was an<br>> >>> adequate limit. 100w is roughly 5% of the average existing DAB<br>> >>> transmitter power, so presuming community stations don't deploy<br>> >>> their DAB transmitters using tethered balloons or satellites etc<br>> >>> they unlikely ever to get near 40% unless they deploy multiple<br>> >>> numbers of transmitters (thus undermining the low-cost aim).<br>> >>> The standard consultation deflection response was invoked (ie:<br>> >>> address a different question) - stating that "it is not<br>> >>> necessarily the case that allowing a higher power will in all<br>> >>> cases reduce the number of transmitters needed". We never said it<br>> >>> would in all cases, but were suggesting that by removing the 100w<br>> >>> cap you retain some flexibility when it /would/ make a difference<br>> >>> in some cases! Unfortunately though, consultations are single shot<br>> >>> - no possibility to clarify the point or challenge the response.<br>> >>> I think we can all imagine the real (unstated) reason why they are<br>> >>> limiting it to 100 watts ;-)<br>> >>> Don't get me wrong - 100w at 200MHz can still provide useful<br>> >>> coverage if planned correctly (other DAB coverage planning<br>> >>> services are available!), but in some cases more may be required.<br>> >>> Otherwise we risk repeating the same problem that analogue CR has<br>> >>> - the paltry standard 25w power is often inadequate and quite<br>> >>> literally blasted off the dial by much stronger commercial and BBC<br>> >>> signals. And this problem is even worse with DAB (for technical<br>> >>> reasons that I will not go into here).<br>> >>> Glyn<br>> >>> --<br>> >>> Glyn Roylance - Principal Consultant<br>> >>> Associated Broadcast Consultants <http://www.a-bc.co.uk/><br>> >>> _______________________________________________<br>> >>><br>> >>> Reply - cma-l@commedia.org.uk <mailto:cma-l@commedia.org.uk><br>> >>><br>> >>> The cma-l mailing list is a members' service provided by the<br>> >>> Community Media Association - http://www.commedia.org.uk<br>> >>> Twitter: http://twitter.com/community_media<br>> >>> http://www.facebook.com/CommunityMediaAssociation<br>> >>> Canstream Internet Radio & Video: http://www.canstream.co.uk/<br>> >>> _______________________________________________<br>> >>><br>> >>> Mailing list guidelines:<br>> >>><br>> >>> http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> >>><br>> >>> _______________________________________________<br>> >>><br>> >>> To unsubscribe or manage your CMA-L mailing list subscription<br>> >>> please visit:<br>> >>> http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br>> >>><br>> >>><br>> >>> _______________________________________________ Reply -<br>> >>> cma-l@commedia.org.uk <mailto:cma-l@commedia.org.uk> The cma-l mailing<br>> >>> list is a members' service provided by the Community Media Association<br>> >>> - http://www.commedia.org.uk Twitter:<br>> >>> http://twitter.com/community_media<br>> >>> http://www.facebook.com/CommunityMediaAssociation Canstream Internet<br>> >>> Radio & Video: http://www.canstream.co.uk/<br>> >>> _______________________________________________ Mailing list<br>> >>> guidelines:<br>> >>> http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> >>> _______________________________________________<br>> >>> To unsubscribe or manage your CMA-L mailing list subscription please<br>> >>> visit: http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br>> >>><br>> >>><br>> >>> _______________________________________________<br>> >>><br>> >>> Reply - cma-l@commedia.org.uk<br>> >>><br>> >>> The cma-l mailing list is a members' service provided by the<br>> >>> Community Media Association - http://www.commedia.org.uk<br>> >>> Twitter: http://twitter.com/community_media<br>> >>> http://www.facebook.com/CommunityMediaAssociation<br>> >>> Canstream Internet Radio & Video: http://www.canstream.co.uk/<br>> >>> _______________________________________________<br>> >>><br>> >>> Mailing list guidelines:<br>> >>> http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> >>> _______________________________________________<br>> >>><br>> >>> To unsubscribe or manage your CMA-L mailing list subscription please<br>> >>> visit:<br>> >>> http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br>> >><br>> ><br>> > _______________________________________________<br>> ><br>> > Reply - cma-l@commedia.org.uk<br>> ><br>> > The cma-l mailing list is a members' service provided by the Community<br>> > Media Association - http://www.commedia.org.uk<br>> > Twitter: http://twitter.com/community_media<br>> > http://www.facebook.com/CommunityMediaAssociation<br>> > Canstream Internet Radio & Video: http://www.canstream.co.uk/<br>> > _______________________________________________<br>> ><br>> > Mailing list guidelines:<br>> > http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> > _______________________________________________<br>> ><br>> > To unsubscribe or manage your CMA-L mailing list subscription please visit:<br>> > http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br>> <br>> _______________________________________________<br>> <br>> Reply - cma-l@commedia.org.uk<br>> <br>> The cma-l mailing list is a members' service provided by the Community Media Association - http://www.commedia.org.uk<br>> Twitter: http://twitter.com/community_media<br>> http://www.facebook.com/CommunityMediaAssociation<br>> Canstream Internet Radio & Video: http://www.canstream.co.uk/<br>> _______________________________________________<br>> <br>> Mailing list guidelines: http://www.commedia.org.uk/about/cma-email-lists/email-list-guidelines/<br>> _______________________________________________<br>> <br>> To unsubscribe or manage your CMA-L mailing list subscription please visit:<br>> http://mailman.commedia.org.uk/mailman/listinfo/cma-l<br></div></div>                                            </div></body>
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